Method of and apparatus for producing bituminous emulsions



y 5, 1932- KIRSCHBRAUN 1,866,503

METHOD OF AND APPARATUS FOR PRODUCING BITUMINOUS EMULSIONS Filed Aug. 24. 1929 2677655, fize//ziar.

. J65 (227125919072 rafiufz "7 Patented .luly 1932 UNITED STATES nnsrna xmscnnmuu, or- LEONIA, NEW JEBsEY' METHOD 01 AND APIABATUS FOB PRODUQING BITUMINOUS EMULSIONS Application filed. Air un a4, 1929. Serial No. 888,062.

This invention relates to improvements in the production of aqueous bituminous emulsions and is more particularly concerned with improvements in the production'of aqueous dispersions ofthe type disclosed in my prior gzgtpnt No. 1,615,303 granted January 25th,

Accordingto the process set forth in the above mentioned patent, bituminous materials, such as asphalt and the like, in heat liquefied condition, are dispersed by subjectpigments, slate dust, powdered metallic 0xides, hydroxides and silicates or the like.

In the commercial manufacture of aqueous bituminous emulsions of the type set forth,

it is essential that the bath of material in which the dispersion is. being eiiected, be maintained 'at suitably controlled temperatures such as will provide a medium of sufficient viscosity to produce that degree of internal viscosity which is necessary to efiect the desired degree of attenuation of the bitumen by what may be pictured as an interfacial trituration thereof. For this purpose, the temperature of the bath will depend largely upon the character of bitumen being emulsified. but in general it may be stated that the temperature of the bath should approximate the melting point of the bitumen, and at all events not more than approximately 10 degrees F. above the melting point thereof.

In the commercial practice of the process set forth in said patent, the temperature of,

the bath may be maintained at a suitable point by providing the emulsifying vessel with pickets for circulating a temperature regu1ating medium and/or by adding water from time to time to the material in the vessel.

I have found in actual practice that it is quite difficult to maintain at all times the proper conditions of temperature in the emulsifying vessel, when the asphalt or other material to be emulsified is fed in heat liquefied condition directly to the emulsifyin vessel at a temperature considerably above t e temperature of the mass in the vessel. Under these conditions, particularly when the asphalt is fed at a rapid rate, it frequently happens that local coalescence of emulsified particles occurs in the vessel where the hot molten asphalt strikes the material therein, causing considerable agglomeration of these emulsified'particles, which must be overcome by additions of substantial quantities of water,

thus resulting in the production of an emulsion containing more than the optimum amount of water in the external phase. It will be appreciated, of course, that it is desirable to produce an emulsion containing a minimum quantity of water in the external phase for any degree of dispersion, consistent with suspendable product.

According to my present invention, the control of temperature is facilitated, the production rate increased and the process otherwise improved by the provision of a cooling stage for the molten asphalt immediately prior to its introduction into the emulsifying instrumentality, such that the asphalt may be reduced to a temperature about 50 degrees to 100 degrees F. above the temperature of the mass undergoing emulsification in the emulsifying instrumentality. This differential of temperature between the incoming asphalt and the mass undergoin emulsification I have found to be the opti mum for insuring proper temperature control and for otherwise improving upon the commerc'ialmanufacture of this type of emul: sion. This diiferential of temperature will obviously vary somewhat, depending upon the consistency of the asphalt, the rate of heat radiation from the emulsifying apparatus and the frictional heat developed duringemulsification. V

In the accompanying drawing, there is Eli shown a diagrammatic illustration of apparatus that may be employed in carrying out the invention.

Thefbase to be emulsified preferably consists of a bitumen, nonfluid at normal temperatures, such for example as asphalt, pitches, or the like, having melting points of say 100 degrees to 200 degrees F. These materials are emulsified in heat liquefied condition but, as already stated, it is the purpose of my invention to bring them to the emulsifying bath at a temperature not more than about 50 degrees to 100 degrees F. above the melting point thereof. In order that these materials may be conveniently handled and conducted through pumps from one point to another in the emulsifying plant, it is necessary that they be heated to a temperature sufficiently high for rendering them fluid enough to permit pumping through pipes, etc., and this temperature 1s generally con siderably higher than that at which it is desirable to introduce the same into the emulsifyin g bath.

For example, when emulsifying asphalt of say 140 degrees F. melting point, (ball and ring method) the asphalt must be heated to about 300 to 325 degrees F. in order to condition it for ready handling. The asphalt may be heatedto this temperature in any convenient way, and conducted by means of pumps (not shown) through a feed line 10 to a storage tank 11. This asphalt may be emulsified in an emulsifier of the general type r shown at 12, which may consist of a cylindrical tank, within which is mounted a baflie 13 concentric with and spaced from the walls of the tank and open at its upper and lower ends. Suitable stirring or agitating blades 14 are fixed upon a vertical shaft 15 driven from any suitable source of power, and mounted interiorly of the bafiie so as to agitate the mass of material in the emulsifying vessel. I

The emulsifying media may be stored in a suitable receptacle 16 and conducted to the emulsifying instrumentality through a valved pipe 17 so as to feed the suspension of emulsifying media into the material undergoing agitation within the baflieo The asphalt is likewise fed into the mass ofmaterial within the bafile through a feeding pipe 18, after previously having been cooled, in the manner hereinafter to be more fully described, to a temperature of about 50 degrees F. above the temperature of the mass in the emulsifying instrumentality. The propeller or agitator blades 14 are pitched so as to force the material undergoing agitation within the bafile downwardly, the material then taking an upwardcourse in the annular space between the bafiie' and the wall of the tank 12 and being I thus recirculated for further agitation within thebaiile. The finished emulsion may be withdrawn from the tank 12 continuously or in the chamber 21, the diameter of this drum or cylinder being such inv relation to the height of the chamber 21 that a portion only of the peripheral surface of the drum is submerged within the molten asphalt in the chamber during the rotation of the drum. A suitable cooling or refrigerating medium may be continuously circulated through the interior of the the drum 23 may be provided with an internal concentric cylinder (not shown), and the cooling medium circulated through the annular space between the outer and inner drums. The drum 23 is rotated slowly and during such rotation picks up a thin film of the asphalt from thechamber 21, this film be ing rapidly cooled to the desired degree by means of the cooling medium circulating in the interior of the drum. A doctor blade or apron 26 is suitably mounted so as to be in free contact with the surface of the rotating cylinder to thereby remove the cooled asphalt continuously therefrom and discharge the same as shown into the enlarged chamber 20, the doctor blade for this purpose having its outer edge extending beyond the corresponding wall of the smaller chamber 21 and being inclined downwardly so as to permit free flow of the cooled asphalt over the surface of the blade for continuous delivery to the enlarged chamber. The flow of asphalt from the storage tank 11 to the chamber 21 is maintained in such ratio relative to the withdrawal of the cooled asphalt from chamber 20 through the pipe 18 that the level of the asphalt in the enlarged chamber will preferably be at all times below the bottom of the smaller chamber 21, thus avoiding material transfer of heat from the hot asphalt in the chamber 21 to the cooled asphalt in the enaa eaoos ing bitumen and without afiecting the normal plant procedure incident to the ready and convenient handling and transfer of the material to be emulsified through pumps, feed lines, etc. a

I claim as m invention:

In the art 0 producing aqueous emulsions of bitumen, non-fluid at normal temperatures, the steps which comprise heating the bitumen to a temperature sufficient to permit it to be fed as a fluid stream, feeding thethus heat liquefied bitumen to an emulsifying zone and cooling the bitumen just prior to its introduction to the emulsifying zone to a. point less than 100 F. above the temperature of the mass undergoing emulsification in said zone, said heating of the bitumen being insuflicient to decompose the bitumen, whereby the viscosity of the bitumen at a 'ven temperature after said heating step wifi be substantially the same as its normal viscosity at said temperature before said heating step and whereby the melting point-penetration characteristics of said bitumen will be substantially the same before and after said heating step, the

temperature of the mass undergoin emulsification in said zone being constant y maintained at a point approximating the melting point of the material to be emulsified, without substantial variation of that temperature due to the temperature of the incoming bitumen.

LESTER KIRSCHBRAUN. 

